Or use your numpad keys as follows:
8 - UP
5 - DOWN
4 - LEFT
6 - RIGHT
0 - PAUZE

If you have 3 or more of the same symbols on a row (horizontal, vertical, diagonal),
they will disapear and you will get points for it.
You start in arcade style, but you can also use custom settings.
Press "Start with new settings" to activate them.
The harder the settings (except speed, speed has no inpact), the more points you get.
Try to get as many points as possible!